Quietshield Gaskets & Shielding flexible, conformable and Fabric-Over-Foam Gaskets are low cost, soft and easy to apply. These gaskets are lightweight Quietshield available in a variety of materials and profiles, including rectangular, D shaped, products deliver effective FL shaped and DD shaped FC68-FC69 EMI shielding across seams Waved Metal and Fabric-Over-Foam or gaps within an enclosure I/O Gaskets are flat products used to provide a ground contact between a metal connector and the electronic enclosure or mating connector FC70 Shielding Tapes and Fabrics are flexible, lightweight, and easy-to-install shielding materials offering high conductivity with a low electrical resistance and are available in a variety of fabric styles FC71 Wire Mesh Gaskets are available as all mesh or elastomer core mesh gaskets. They provide excellent heat and corrosion resistance and are used between two surfaces to maintain electrical continuity while shielding electromagnetic waves FC72 Conductive Silicone is used for its heat resistant properties and can be produced in many different forms such as sheets, molded parts, die-cuts or strips. These conductive elastomers are water resistant, can eliminate static electricity, and act as an absorber at high frequencies FC73 FC65Shielding Theory and Introduction Shielding Theory The shield will continue to function as long as there are Electromagnetic shielding is used to prevent electromagnetic no holes in the electromagnetic shield which would allow signals such as radio signals from leaving or entering a box the currents to flow from one side of the shield to the other. or enclosure. Signals inadvertently emitted by an electronic Holes are a necessity in an electronic enclosure. Connectors, device can cause distortion or interruption in normal radio wires, and cables are needed to transmit information to and communications in a localized area. This is the basis of from electronic devices. Doors and covers are needed to most laws and regulations concerning electromagnetic get access to components to maintenance, service, and interference. In addition, normal radio signals can cause keypads may also be required. The problem is that all of unprotected electronic devices to malfunction. Depending these items cause openings in the shield which reduce on the devices function, a malfunction in the device could the performance of the shield. be a minor inconvenience such as static on a radio, or life threatening such as the malfunction of a life support system Special devices such as shielding gaskets, shielding at a hospital. ventilation panels, shielded filtered connectors, and shielded switches minimize the effect of a hole in the shield. Introduction The length of the hole and wavelength of the signal that needs to be shielded are the major factors determining The electromagnetic shield in most cases is the electronic the shielding effectiveness of an electronic enclosure. The housing itself. The housing/shield forms a metal cage around distance between spotwelds, or screws which hold a metal the electronic circuits in a device. Most of the electromagnetic housing together count as long narrow holes. Higher frequencies signal is absorbed with a small portion (3 to 10 dB) of the (lower wavelengths) flow more easily through smaller holes, signal reflected off the metal housing. Most of the absorbed and so the highest frequency needed to be shielded is signal creates alternating currents at radio frequencies the frequency of concern when designing shielding. which travels on the surface of metal. This allows the electromagnetic shield to keep signals from outside the Aperture versus frequency charts can give a rough enclosure on the outside of the shield and signals from estimate of the shielding effectiveness of a metallic inside signals on the inside of the shield. electronic housing. SHIELDINGEFFECTIVENESS TYPICAL SHIELDINGEFFECTIVENESS 100. 110 40 dB 20 dB 60 dB 100 Wavelength 90 10. to Frequency 80 80 dB 70 1. 60 50 .1 40 30 .01 20 10 .001 0 100 KHz 1 MHz 10MHz 100MHz 1GHz 10GHz 100GHz 0 100 200 300 400 500 600 700 800 900 1000 Frequency (MHz) Frequency (MHz) Test Methods:ASTM D-4935-89 Test Fixture: Flanged coaxial transmission line API TECHNOLOGIES 8061 Avonia Rd. Fairview, PA 16415 Ph: 814-474-1571 Fax: 814-474-3110 eis.apitech.com FC66 API TECHNOLOGIES SPECTRUM CONTROL GmbH Hansastrasse 6 91126 Schwabach, Germany Phone: (49)-9122-795-0 Fax: (49)-9122-795-58 Aperture Length (Wavelength - Inches) Shielding Effectiveness (dB)